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ASME J of Medical Diagnostics. 2018;1(3):031001-031001-6. doi:10.1115/1.4039560.

We found a significant difference (P < 0.05) between the linear portion of the elastic modulus (∼20 MPa) and tensile strength (∼2 MPa) at the 0.2 mm/s (low: 0.01 s−1), 2 mm/s (medium: 0.11 s−1), and 20 mm/s (high: 1.11 s−1) loading rates by performing a series of uniaxial stretching tests. However, the mechanical properties of the neural fiber bundles were resultantly of the same magnitude, indicating that their mechanical responses were relatively insensitive to a given strain rate regardless of a 100-fold increase in the applied stretching velocities. We also confirmed that a “spinal level effect” exists in the nerve roots, i.e., a fiber bundle isolated from the lumbar spinal level is weaker in mechanical strength compared to that from the cervical and thoracic spinal levels (P < 0.05), suggesting that closer attention should be paid to an anatomical site from which test samples are excised.

Commentary by Dr. Valentin Fuster

Expert View

ASME J of Medical Diagnostics. 2018;1(3):034701-034701-7. doi:10.1115/1.4039561.

The use of reference ranges is well established in medical practice and research. Classically, a range would be derived from the local healthy population and matched in age, gender, and other characteristics to the patients under investigation. However, recruiting suitable controls is problematic and the derivation of the range by excluding 2.5% at each end of the distribution results in 5% of the values being arbitrarily discarded. Thus, the traditional reference range is derived using statistical and not clinical principles. While these considerations are recognized by clinicians, it is often not realized that the application of whole population derived reference ranges to complex pathologies that comprise patient subgroups may be problematic. Such subgroups may be identified by phenotypes including genetic etiology, variations in exposure to a causative agent, and tumor site. In this review, we provide examples of how subgroups can be identified in diverse pathologies and how better management can be achieved using evidence-based action limits rather than reference ranges. We give examples from our clinical experience of problems arising from using the wrong reference ranges for the clinical situation. Identifying subgroups will often enable clinicians to derive specific action limits for treatment that will lead to customized management and researchers a route into the study of complex pathologies.

Commentary by Dr. Valentin Fuster

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